For many years, hand tools such as crimpers, cutters and other plier-like tools have been manufactured in a forging process from both ferrous and non-ferrous metals depending on the application of the tool. While this process is capable of producing handle blanks with good structural qualities, it has many disadvantages. One disadvantage is that not all materials are suitable for the forging process which limits the ability to utilize the ideal material for a particular application of the hand tool. Another disadvantage is the expense of the equipment required to produce the necessary compressive forces and the high temperatures needed to forge the metal into the desired shape. Furthermore, the dies employed are expensive because they must be capable of withstanding repeated exposure to these high compressive forces and high temperatures.
Another disadvantage is the cost associated with producing the handle blank. In addition to the above, the forging process typically requires many cycles from the forging hammer or hammers to form the metal into the desired shape. This reduces the rate at which handle blanks can be produced thereby increasing the cost per handle blank and reduces productive availability of the expensive equipment. As a result of the equipment, the forging dies and the temperatures involved, the forging process is also not well adapted for short run sizes which increases costs associated with inventory and scrap.
Still another disadvantage is the expense associated with machining the handle blank after the forging process. The forging process is not well adapted to accurately producing intricate shapes or contours. Therefore, expensive secondary operations are required to produce the working surface of the hand tool. These operations typically require precise cutting or machining to produce these working surfaces by specialized equipment, tooling and by highly skilled operating personnel. The machining of these working surfaces by trained personnel is a very laborious and tedious task, and therefore, a costly labor intensive operation. It is often necessary to provide special cooling techniques within the equipment to control the temperature associated with metal removal to prevent adverse affects to the structure of the metal. This is especially difficult with respect to machining intricate curves or other contours.
Another method of producing hand tools utilizes flat sheet stock that is stamped to produce the handle blank. A stamping die is typically used to produce the edge geometry from the sheet stock which results in a handle that has a substantially uniform thickness based on the thickness of the sheet stock. While this process reduces much of the cost associated with forging handle blanks, it also has many disadvantages associated with producing many types of crimpers, cutters and other plier-like tools. While many materials can be stamped, many are not well suited for the stamping process. Materials that have properties that are advantageous to produce a durable hand tool, such as high carbon steels, can often cause premature die wear or die failure.
Even though the stamping process is capable of producing edge geometry, its ability to produce an accurate edge geometry, capable of use as a working surface, is limited. One limitation is that high volume dies do not have the accuracy required to repeatedly produce the dimensional requirements of many working surfaces. Furthermore, the stamping process does not produce a clean flat edge unless expensive, fine blanking techniques are used. This condition is worsened as the thickness of the sheet stock is increased. In some cases less than 20 percent of the edge is flat while the remainder is either rounded or ragged. As a result, these surfaces must be machined if they are to be used as a working surface.
Another disadvantage is the limited ability to produce shapes or contours other than edge geometry. As stated above, the stamping process is mainly utilized to create only the edge geometry that has a uniform thickness based on the thickness of the sheet stock. While this is effective in producing the general handle shape, secondary operations are utilized when contours or shapes are required to change the thickness of the sheet stock or produce a component that is not generally flat. This can include a secondary stamping operation to bend or form the handle blank, such as to make the handles or jaws line up when a lap joint is used to assemble the two handle blanks. In addition, the handle blanks may require machining if the working surface includes a tapper or if a cutting edge is to be produced. As discussed above, these secondary operations are expensive and require highly skilled operators.
In recent years, it has been found that hand tools can be constructed of a plurality of laminations. A considerable time and cost savings has been realized by constructing hand tools in this manner rather than from forged material or by stamping. Machining steps utilized to remove excess material or to clean up rough edges associated with stamping heavy gauge material can be considerably reduced or eliminated. The laminations are produced individually to a predetermined edge contour and then stacked in the proper sequence to form the desired thickness. Once stacked in the proper sequence, they are suitably fastened together to form an integral unit. Typically, they are fastened together by rivets. The edge geometry may be cut by utilizing standard machining or stamping techniques, or they can be cut by a laser beam, plasma cutters or other suitable cutters, as is well known in the art. By stamping thinner gauge metal, a better edge quality is produced wherein there is less roundness and raggedness. Furthermore, if stamping dies are utilized, they are subjected to lower forces due to the thinner material which allows smaller less expensive dies to be utilized and promotes longer die life.
The laminating method fails to overcome many of the disadvantages associated with stampings as discussed above. While edge geometry is improved, the edge still includes rounded and ragged portions. Even though the amount of non-flat edge is reduced, a "step effect" is produced wherein the edge portion of each lamination includes a rounded portion, a flat portion and a ragged portion. This results in a repeated pattern of rounded, flat, ragged, rounded, flat, ragged, etc. corresponding to the number of laminations utilized. Many working edges still require the edge of the laminate to be machined in order to produce a predominantly flat edge.
It will be appreciated that the thickness of the laminations has considerable effect on the roundness and raggedness of the edges and the strength of the part. The thinner the laminations, the smaller the "step effect" created, and the less metal removal that is required to finish the edge surface. Thus, to manufacture a laminated tool requiring a minimum of finish machining after assembly, it maybe desirable to employ laminations as thin as practical for the contour of the handle being produced. Obviously, the use of thinner laminations results in an increase of the number of laminations utilized, resulting in an increase in stamping costs, in time expended on the initial handling and in the assembling of the parts.
The laminated method of construction is also not well suited for producing shapes or contours other than the edge geometry of a flat component. As discussed above, the stamping process is best suited for producing only edge geometry with a uniform thickness based on the sheet stock. The laminating process does little to solve this problem. Therefore, costly machining operations are still utilized to produce working surfaces that include tappers or other contours that alter the thickness of the sheet stock. This is especially true when dimensional accuracy is critical.
Another disadvantage with each method discussed above is that the jaw assembly is integral with the handle being formed and/or machined out of the same part. As a result, the handle portion and the jaw portion of the tool are made of the same material. It is well known in the art that the optimal material for any component is based on its application. In addition, the optimal surface finishing or heat treatment is determined by the application. It is common for the jaw portion of a hand tool to have a different optimal material, finish or heat treatment than the handle portion. For example, while the working surface of a jaw might require a surface hardness of over 60 R.sub.c to maintain its shape, it may be desirous for the corresponding handle portion to have a low Rockwell Hardness so that it will yield under a heavy load versus fracturing. Therefore, when handles and jaws are created from one component, a compromise must be made. Typically, the material is chosen based on the needs of the working surfaces, but this causes the handles to be made of expensive material which adds unnecessary costs to the tool. This is emphasized by the fact that the handles of a tool typically require the greatest amount of material.
Some tools have utilized a separate jaw assembly that is riveted or screwed to the handle to produce the finished part. Rivets or screws are utilized to withstand the forces produced or the general usage requirements for a plier-like assembly. However, rivets or screws add to the overall cost of the tool as well as the manufacturing time in assembling the tool. In addition, it is advantageous that a jaw portion be as compact as possible to allow access to confined work spaces. Rivets and screws can adversely increase the overall size of the jaws.